Ultrasound imaging machines include a transducer probe that includes piezoelectric crystals to generate sound waves and also detect the reflected waves. In a conventional ultrasound machine the transducer probe is connected to an external processing box by a cable, where the external processing box has electronics to generate high frequency voltage pulses sent to the transducer probe, receive detected signals from the transducer probe, and perform signal processing and scan line conversion to reconstruct the image.
Referring to FIG. 1, in a conventional ultrasound imaging machine the cable is typically several meters long (e.g., 2 m) and contains 48 to 256 micro-coaxial cables, where the number of micro-coaxial cables scales with the number of transducer elements in the transducer probe. The micro-coaxial cables are expensive and have other disadvantages. In particular, the micro-coaxial cables introduce a cable loss and a cable impedance. For example, a conventional 2 m cable might have a capacitance of 203 pF, while a transducer element could have a capacitance on the order of 5 pF. Additionally, a 2 m cable may introduce a 2 dB attenuation. The cable introduces a large capacitive loading, which makes it impractical to perform fine grained apodization of the transmitted voltage pulses sent to the transducer probe.
In ultrasound systems the spatial resolution of the image is determined by the size of the piezoelectric crystal (“crystal”) elements of the transducers and the number of such crystal elements. Higher resolution typically implies smaller crystals and larger crystal arrays. Larger crystal arrays lead to more expensive systems and limitations on the physical layout and cabling of the system. In particular, the number of micro-coaxial cables required increases with the number of crystal elements. Thus, in the prior art increasing spatial resolution requires more crystal elements and more complex and costly cables.
Thus, ultrasound imaging systems are more expensive than desired. This is due, in part, to need for a large number of transducer crystals and the cost and complexity of the micro-coaxial cables and associated electronics. For example, in 2014 a commercial ultrasound imaging system may cost $30-50 k. Additionally, another problem in the prior art is that quality of the scan line processing to reconstruct the ultrasound image is poorer than desired. In particular, the scan line conversion at the distal end of the ultrasound beam results in poor resolution due to a lack of signal strength, loss of beam focus, and inadequate spatial binning.
The present invention was developed to address the above described problems in the prior art.